Debating evolution

SCIENCE'S world view is usually said to be cold and abstract, but in fact it offers a far more exciting, if more threatening, image than the Biblical account of the creation of the world. In his latest book, The Evolutionists: The Struggle for Darwin's Soul, [+] Richard Morris, a scientist of wide-ranging knowledge, presents what has become the standard scientific view of the origins and development of the world and its life. A reader could ask for no better introduction to the increasingly important, and increasingly complex, evolution debates.

As science explains it, the Earth was created over four billion years ago when stellar dust and rocky fragments collided to create a molten sphere. Volcanoes exploded through its skin and tectonic plates shifted, pushing up great mountains and creating deep canyons. The atmosphere was alternately boiling hot and icy cold, with huge glaciers replacing empty deserts. Great winds and vast oceans ate at the land's shores. Whirling about a distant sun, bombarded by sterile meteors from space, the Earth was light-years away from its nearest stellar neighbors.

Living things, as Morris explains, appeared about 3.5 billion years ago, and since that time have been no more fixed than the Earth itself. Old species died out, sometimes killed off by natural catastrophes like the great meteor that slammed into the Yucatan 65 million years ago and wiped out the dinosaurs. Hominids are estimated to have appeared about 1.5 million years ago, and our species, homo sapiens, only about a hundred thousand years ago.

We long for stability, but science has given us a world of endless variety, one in ceaseless movement but without direction. Charles Darwin's principle of natural selection, as outlined in his Origin of Species, published in 1859, provided the only vector that we have had in this vivid infinity of violent change. Natural selection is still at the heart of the orthodox view of evolution, describing how the environment determines which of Nature's variations will succeed and procreate, and which will fail to survive because of a misfit with the circumstances in which they appear. For example, a shift in rainfall patterns may turn a jungle into desert and thereby threaten an entire species unless some variant, such as a finch with a longer beak, can adapt to the new circumstances.

During Darwin's lifetime, Gregor Mendel, an obscure Augustinian monk hybridizing peas in the garden of his Bohemian monastery, made visible the workings of genetics. Genetics would in time show that species ran true to type rather than combining traits, and that they threw off variants that would be tested by natural selection. Although Mendel published his findings, Darwin never read them. It was not until this century that genes were actually located and seen, and the science of genetics began to take shape. In recent years, genes have come to be accepted as the source of new life forms, continually tested and refined by natural selection. Thus the "origin of species" is a twofold process, explained as much by mutating genetic codes as by the natural selection that Darwin described. Certainly, after the genetic revolution, and especially now with the human genome mapped, the origin of species is no less than an interaction of the two, one "proposing" and the other "disposing."

DARWINIAN natural selection is still orthodoxy, but the of ideas is no more immune to change than the globe itself or the animals and plants that inhabit it. Morris describes in close detail a scientific war between orthodox evolutionists who understand natural selection to be the determining force behind species survival, and other leading scientists who, while still conceding priority to natural selection, offer other ways of accounting for the ceaseless change in forms of life and their activities.

Richard Dawkins, author of The Selfish Gene, and philosopher Daniel Dennett are among the leaders of "the evolutionary fundamentalists," who, following the traditional modus operandi of science, proclaim a single truth--natural selection--to explain all natural phenomena. They are sometimes styled "Panglossians" by their opponents, after the pedant in Voltaire's Candide who teaches that despite its untold misery, ours is the best of all possible worlds. Their attempts to prove natural selection by inventing survival functions for every trait they encounter have been mockingly labeled "just-so stories."

Their opponents, "the revolutionaries" or the "evolutionary pluralists," are led by Harvard molecular biologist Steven Jay Gould, his colleague Richard Lewontin, and Niles Eldredge, a paleontologist at the Museum of Natural History. Morris characterizes Gould and his supporters as evolutionary "holist[s] who believe that reductionism is not sufficient, that interesting new phenomena emerge at higher levels of complexity."

IN part because he writes so well, Gould has become the authority on evolutionary matters, at least in the United States. He still believes, or claims to believe, that a blind natural selection is the primary force in evolution. But Gould also wants other forces, such as "spandrels," to be recognized. These are traits and abilities like reading which have themselves no immediate survival value, but are by-products of developments that do have survival value, like a relatively large human brain. In other words, natural selection continues to operate, but other forces play a part in the creation of new traits and new species. Where strict Darwinians see a steady appearance of new species, Gould looks at the fossil record--incomplete as it is--and sees long periods of stability followed by brief, intense times of change, a pattern that he calls "punctuated equilibrium." Punctuated equilibrium allows Gould to speculate that some unknown force lies behind the change of species, one that makes itself known in sudd en concentrated changes. Whatever the particular approach, Gould always seeks out the broader view, the variety in the system, and what he therefore offers is a more open, and less determined pattern of evolution than that of the strict Darwinians.

Gould has had numerous allies in this effort, for the questions concerning evolution involve all aspects of modern science and a lot of politics as well. Morris describes a number of these fascinating developments. Take, for example, "complexity science," in which scientists abandon the standard reductive scientific principle, that is, one model or simple unit, such as the quark or Chomsky's universal hard-wired grammar, upon which all else is based. Complexity scientists instead look at an entire field of phenomena and assume that all parts interact with one another to create new and unexpected results, results that they believe no single force could have created alone. Perhaps the most striking example of complexity science that Morris offers is the ant colony. Each individual ant is extremely limited in what it can do, but the ant colony as a whole performs a multiplicity of functions ranging from milking aphids to capturing slaves from neighboring colonies. These activities are the product of the needs o f a complex group, not the interests of a single individual.

Complexity science, though new, already offers a very different explanatory framework than does the strict pattern of genetic mutation and natural selection. In the latter system, new species appear at a fairly steady rate and are then tested by the environment, which either permits them to flourish or discards them. From the view of complexity science, things accumulate, interact, and, at least in some cases, produce systems with new and unexpected features. Language offers an excellent example of this process. Take the few vowels the human voice is capable of, or the 50 some sounds of the phonetic alphabet, and out of them grows the wondrous world of language. Language can, of course, be explained by a "just-so story" of how it furthers survival, but it would be a limited and strained argument at best.

OURS is a time when all things are said to be political. Evolution, Morris points out, is no exception. Gould has been charged with being either a Marxist or a crypto-religionist for seeking to alleviate Darwin's raw and meaningless struggle for survival with humane intervention. Gould denies any political or religious bias to his science, but it does obviously appeal to the liberal view of life far more than other evolutionary theories. In contrast, strict natural selection better fits a conservative perspective, one that seeks absolute rules and accepts that life is hard, always at risk, and at times beyond human control. The conservatism of natural selection is most apparent in the sociobiology of Gould's antagonist, E. 0. Wilson, who traces all human activity back to primary traits that are locked into our genes by the iron law of necessity: Only that which works survives.

Gould and his allies want some wiggle room, some possibility of getting out of the bind of natural selection. Their biology synchronizes best with the standard social science model in which humans 'escape' nature into a more hospitable manmade culture. Morris offers as an example of this kind of social science Margaret Mead's studies of cultures in Samoa and New Guinea. According to Mead, these societies reversed the most familiar human sexual practices. Her noble savages practiced free sex from an early age, didn't feel sexual jealousy, and allowed women the same sexual freedom that, at least in most societies, men alone possess. Modern feminists and gay-rights advocates share Mead's belief that sex is only a matter of culture and is therefore open to limitless variation and purposeful change. Most conservatives still argue, however, that nature trumps culture and that the monogamous female and the polygamous male are "hard-wired" roles, reinforced by tradition and by reproductive success.

ONLY facts can settle questions about how life has come to take its present forms. But new facts are hard to come by in evolution, given the relative slowness with which species change and adaptations appear. One has to admire Stuart Kauffman, a theoretical biologist discussed by Morris, who in the absence of natural facts has set up and run a computerized model of evolution. Although his "Ancestor has only a few "genes," and his genes only a few "traits" instead of the three billion "letters" of the human genome, Kauffman sends them merrily on their digital way, covering billions of years in foreshortened computer time, going down many alleys, blind and otherwise. It is on this computer that he runs his digital evolutions, although so far his results have been "inconclusive." He certainly has not been able to tell us why deafness, surely a feature with negative survival value, has not yet eliminated the white-furred cats with which it is linked.

ALVIN KERNAN is author of In Plato's Cave (Yale University Press, 1999) and is at work on The Fruited Plane: Satires on Y2K America.

(+.) W.H. Freeman & Co. 262 pp. $22.95.

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